Protective wall panel assembly

ABSTRACT

An assembly of wall panels particularly suitable for protection against wind blown debris or an explosion includes a bent strap connecting an air gap between adjacent wall panels with the bent strap capable of flexing due to a sudden external force.

TECHNICAL FIELD

[0001] The invention relates to a method for the assembly of protectivewall panels using a bent strap-joint to provide improved resistance toimpact loads such as generated by severe storm events and explosiveblasts.

BACKGROUND OF THE INVENTION

[0002] Storm and blast shelters are necessary to provide a safe havenfor civilian protection against severe storm events in regions prone totornado or hurricane activity and military protection from explosiveblast events. Protective wall and building designs are known in the artand take on various forms. Wall designs proposed for severe storm eventsare detailed in various reports developed for, or by, the FederalEmergency Management Agency (FEMA). Various wall designs for blastresistant shelters are detailed in patent art.

[0003] In Taking Shelter from the Storm (FEMA Publication 320) andDesign and Construction Guidance for Community Shelters—(FEMAPublication 361) design for construction of walls and buildings toresist tornado generated wind loads and debris impact are described.Wind impact resistant walls of other designs are detailed in a reportdated May 31, 2000 by Clemson University submitted to the FederalEmergency Management Agency entitled “Enhanced Protection for SevereWind Storms. While these designs do not meet Tornado Impact criteria,they do provide enhanced protection from less severe storms.

[0004] U.S. Pat. No. 3,994,105, U.S. Pat. No. 4,143,501, U.S. Pat. No.4,566,237, U.S. Pat. No. 4,691,483, U.S. Pat. No. 4,748,790 and U.S.Pat. No. 4,937,125 each detail some of the various forms for blast andbullet resistant walls and buildings.

[0005] Many of these engineered wall systems provide the capability toproduce modular wall systems that are subsequently assembled in thefield for use. When such modular approaches are used, a simple fieldjoint that enables easy assembly provides for structural load transferand yet provides impact resistance is desirable.

[0006] It is well known in the art that if some flexibility can beengineered in the direction of impact, that such flexibility willimprove overall impact resistance. The various wall designs in the artthat have such flexibility must be joined together in a manner that doesnot restrain the movement of these wall systems, especially near thepoint of attachment. This is most critical near joints where walls abutone another at corners or other non-planer joints where one wall cansubstantially restrain the movement of the other.

[0007] A substantial need exists for a method for the assembly ofprotective wall systems for wind and blast resistance that providesimproved flexibility between wall segments. A particular need exists fora joint between non-planer wall segments that is easily assembled in thefield and provides improved flexibility.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to an assembly of wall panelsparticularly suitable for protection against wind blown debris or anexplosive blast comprising;

[0009] (a) at least two wall panels positioned in a non-planerorientation to one another wherein an air gap is present between twoadjacent wall panels;

[0010] (b) at least one bent strap spanning the air gap between twoadjacent wall panels wherein the bent strap is rigidly connected toadjacent wall panels and wherein the strap is capable of flexing due toan external force on a wall panel such as from an impact resulting fromwind blown debris or an explosive blast.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a schematic of a shelter system of Example 1.

[0012]FIG. 2 is a schematic of wall positions connected by strapping ofExample 1.

DETAILED DESCRIPTION OF THE INVENTION

[0013] In the present invention it is necessary to employ at least onewall panel capable of withstanding a force generated from a suddenimpact such as wind blown debris of from an explosion. The types of wallpanels are varied and can be formed from a metal such as steel, fromwood or from a composite of several different materials. Althoughtypically there will be wall damage due to an impact, the purpose of thewall is to maintain its integrity such as to protect a person within aroom of a building. Although only one impact resistant wall panel can beemployed to protect against an external force, it is desirable forgreater protection to employ two adjacent wall panels to have impactresistance.

[0014] The protection from a wall panel will depend on its construction.The greater the ability to withstand force will in turn offer a greaterprotection. An example of a test procedure to determine impactresistance is ASTM procedure E 1886-97. Illustratively a 33 kilogram (15pound) 2×4 lumber projectile is employed to impact a wall. The abilityof the wall to withstand a projectile speed is a measure of determiningits resistance. A desirable resistance is an at an impact speed of 161kilometers (100 miles) an hour. Less resistance would be at failure atimpact speeds above 80 or 90 miles an hour.

[0015] In similar fashion to determining resistance in accordance toASTM procedure E 1886-97 test procedures to obtain a desired resistanceto a force generated from an explosion can be used to determine the typeof wall panel to be employed.

[0016] For windblown debris a suitable wall constructions are describedin U.S. patent application 09/977,648 filed 15 Oct. 2001 and 10/308,492filed 3 Dec. 2002 incorporated by reference herein. An example of aconstruction is a composite comprising in order:

[0017] (a) a layer of material having a density not greater that 0.10grams per cubic centimeter,

[0018] (b) a layer of a fabric containing fibers bonder with a resin and

[0019] (c) a layer of structural sheathing.

[0020] A necessary portion of the construction of the wall assembly isthe use of a strap to connect adjacent wall panels. As employed hereinthe term strap means a band or plate for holding an object in a fixedposition. Although the strap may be of metal construction, such as steelor aluminum, other materials are suitable such as plastic or a compositeof different materials.

[0021] The strap is rigidly connected to adjacent wall panels and holdsthe panels in place. However, the strap is capable of flexing due to aforce on a wall panel. It is directly understood that the amount of flexof the strap will be determined by its end use. Illustratively, a needfor a greater resistance to an impact will determine a greaterresistance to flex. Also the amount of stap flex will be determined bythe number of straps connecting adjacent wall panel. The greater numberof straps, the lesser is a need for resistance to flexing.

[0022] For purposes of illustration both single and double straps aresuitable. An example of a suitable thickness for a metal strap is from0.06 inches (1.5 mm) to 0.375 inches (9.5 mm) such as 0.075 inches (0.19mm) to 0.150 inches (3.8 mm).

[0023] Although a strap may be employed on only an inner or outer wallportion, preferably individual straps are present to connect adjacentwall panels on inner and outer walls. As employed the term inner meansportions of wall which face one another, such as walls that form theinterior of a room. The term outer means portions of a wall which do notface one another, such as walls that form the exterion of a room. Thestrap or straps connect walls in a non-planer orientation, i.e. the wallare at an angle to one another. For purpose of illustration most wallsare joined at an angle of 90 degrees. An example of two walls joiningone another is an angle within a range from 30 to 120 degrees. Alsogenerally there will be an air gap between adjacent wall since if thewall touch there may be an inability for the strap to flex properly upona sudden impact. A typical air gap is considered to be at least 3 mm(0.125 inches). In a preferred construction a wall capable ofwithstanding a sudden impact is joined to two adjacent wall with strapson both on inner and outer wall surfaces connecting adjacent walls.

[0024] In the above disclosure the combination of a wall assembly withuse of straps has been describe in relationship to resistance andprotection of a sudden impact such as from wind blown debris and anexplosion. However it is within the scope of the present invention thata wall assembly need not possess such resistance. Therefore, wall panelscan be employed with such resistance to an excess sudden impact. In turnthe staps would have the ability to flex under a minimum amount of forceupon one of the wall panels.

[0025] To further illustrate the present invention the following exampleis provided.

EXAMPLE 1

[0026] A shelter system shown in FIG. 1 with external dimensions of 115inches long by 64 inches wide by 94 high was assembled from engineeredwall and roof panels designed to protect occupants from windborne debrisgenerated by tornadic winds. Five wall panels and a modular door unit,each 48-in wide by 88-in high were used. Two ceiling panels that were48-in wide by 48-in long were used for the roof. Panels were producedusing, in order, 1 layer of 3/4-in plywood, followed by a 5-1/2 inchthick steel reinforced expanded polystyrene core with a density of 1lb/cu-ft (0.016 gm/cc), followed by a laminated fabric made from 3layers of a 13 oz/sq-yd aramid cloth that was bonded together with apolyethylene co-polymer resin, followed by one 1 layer of 1/2-inplywood. Steel reinforcement within the core, was done with 24-gauge 2×4common metal framing studs on 16-inch centers that were laid flat oneach face of the panel. Reinforcement was added during the foamingprocess as described in U.S. Pat. No. 4,241,555. The layers of materialwere joined together by fastening with power driven knurled nails drivenon each face of the panel, around the perimeter on 3-in centers andalong the field studs on 6-in centers.

[0027] The panels were assembled as shown in FIG. 2, using two, 11 gauge(0.12-inch thick) sheet metal brackets that were bent in two places with45° angles to create the 90° corner connections required to assemble therectangular shelter. The 1/2 plywood face was oriented outwardly. Three,3/8-in diameter bolts were used to fasten the edges of each panel to themetal strap connector. A space of 3/8-in was present between the cornersof any adjacent panels that were connected.

[0028] The shelter was impacted in several locations with a 15-lb 2×4(inches) timber projectile traveling at 100 mph, to access ability tomeet the “Windborne Missile Impact Resistance on Shelter Wall andCeiling” provisions of the National Performance Criteria for TornadoShelters, First Addition, FEMA, May 28, 1999. Cannon set-up and firingwas done in accordance with ASTM E 1886-97.

[0029] All projectiles fired at the shelter were stopped from passingthrough it, as required by the FEMA provisions, and the projectile wasrebounded back. High speed photography taken during the event showed thejoints to flex inwardly upon impact, helping to absorb a portion of theenergy from the projectile. The plywood layer on the backside showedonly very minor cracking around the impact point. The shelter assemblywas deemed compliant with the provisions of the National PerformanceCriteria for Tornado Shelters.

What is claimed:
 1. An assembly of wall panels comprising; (a) at leasttwo wall panels positioned in a non-planer orientation to one anotherwherein an air gap is present between two adjacent wall panels; (b) atleast one bent strap spanning the air gap between two adjacent wallpanels wherein the bent strap is rigidly connected to adjacent wallpanels and wherein the strap is capable of flexing due to a force on awall panel.
 2. The assembly of claim 1 with individual straps connectinginner and outer surfaces of adjustment wall panels.
 3. The assembly ofclaim 1 with one wall panel connecting to two wall panels withindividual straps.
 4. The assembly of claim 1 where the strap comprisesa band.
 5. The assembly of claim 1 wherein the straps comprises a plate.6. The assembly of claim 1 wherein the strap comprises metal.
 7. Theassembly of claim 6 wherein the strap comprises steel.
 8. The assemblyof claim 6 wherein the strap comprises aluminum.
 9. The assembly ofclaim 1 wherein the strap comprises a composite.
 10. The assembly ofclaim 1 wherein wall panels are positioned at an angle between 30 and120 degrees on to another.
 11. The assembly of claim 1 wherein with agap of at least 0.125 inches (3 mm) between adjoining wall panels. 12.The assembly of claim 1 wherein a single metal strap is used.
 13. Theassembly of claim 1 wherein a double metal strap is used.
 14. Theassembly of claim 1 wherein the straps are between 0.075 inches (0.19mm) and 0.150 inches (3.8 mm).
 15. The assembly of claim 1 wherein onewall panel comprises in order: (a) a layer of material having a densitynot greater than 0.10 grams per cubic centimeter, (b) a layer of afabric containing fibers bonded with a resin, (c) a layer of structuralsheathing. wherein the fabric layer will deflect in a range from 5.0 to17.5 centimeters when impacted by a 33 kilogram (15 pound) projectile ata speed of 161 kilometers (100 miles) per hour in accordance with ASTMtest procedure E1886-97 with said composite mounted on a rigid frame.16. The assembly of claim 1 wherein the strap is capable of flexing dueto an external force from wind blown debris or an explosive blast. 17.The assembly of claim 16 wherein the stap is capable of flexing due todebris at a wind speed of 100 miles per hour.